Over the past decade, nanotechnology has been explored to improve bioavailability, lower side effects, and enhance targeting of therapeutic agents for a wide variety of diseases. When agents are administered systemically, the therapeutic effect is typically lowered by rapid clearance through enzymatic digestion, renal filtration, and mononuclear phagocytic system (MPS) uptake. Encapsulating the agent in nanoparticles (NPs) has been investigated to modulate these factors, as the precisely engineered NPs can protect the agent from rapid clearance but also help it reach the target site more efficiently and preferentially. Widely used materials for producing NPs include polymers, lipids and some inorganic materials. However, encapsulation of therapeutic agents in NPs does not ensure successful delivery. In fact, particulates are often more efficiently cleared from the blood by MPS uptake, particularly by phagocytic cells in the liver, leading to rapid loss of NPs and their associated drugs from circulation, which limits their ability to reach non-liver targets.
It is well-known that surface modification of NPs with substances that prevent non-specific adsorption can reduce their interaction with serum proteins and increase the blood circulation of the NPs. An ideal surface coating resists non-specific adsorption of proteins and facilitates the attachment of other functionalities, such as targeting ligands, to the particle. To resist non-specific adsorption in physiological conditions, materials for coating are usually charge neutral, hydrophilic, and stable in physiological environments. Among the few materials used as coating for NPs, PEG has become ubiquitous. The advantages of PEG as a coating of NPs for drug delivery include its low toxicity, low immunogenicity, and resistance to non-specific adsorption of biomolecules. PEG has so dominated the field of surface coatings that new approaches are rarely investigated.
However, PEG has considerable limitations. For instance, it is known that PEG chains can adopt a variety of configurations on the surface, depending on PEG surface density, and the most effective densities are often difficult to achieve.
There exists a need for particles with improved coatings, in which the coatings can be tuned to provide stealth or adhesive properties and can further be modified with targeting moieties, and which overcome the limitations associated with polyethylene glycol coatings.
Therefore, it is an object of the invention to provide particles with improved coatings, in which the coatings can be tuned to provide stealth or adhesive properties and can further be modified with targeting moieties, and which overcome the limitations associated with polyethylene glycol coatings.